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ceph: make sure mdsc->mutex is nested in s->s_mutex to fix dead lock

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send_mds_reconnect takes the s_mutex while the mdsc->mutex is already
held. That inverts the locking order documented in mds_client.h. Drop
the mdsc->mutex, acquire the s_mutex and then reacquire the mdsc->mutex
to prevent a deadlock.

URL: https://tracker.ceph.com/issues/45609
Signed-off-by: Xiubo Li <xiubli@redhat.com>
Reviewed-by: Jeff Layton <jlayton@kernel.org>
Signed-off-by: Ilya Dryomov <idryomov@gmail.com>
This commit is contained in:
Xiubo Li 2020-05-20 03:51:19 -04:00 committed by Ilya Dryomov
parent 878dabb641
commit ea8412b284
1 changed files with 2 additions and 2 deletions
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4
fs/ceph/mds_client.c
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@ -3769,8 +3769,6 @@ fail:
* recovering MDS might have.
*
* This is a relatively heavyweight operation, but it's rare.
*
* called with mdsc->mutex held.
*/
static void send_mds_reconnect(struct ceph_mds_client *mdsc,
struct ceph_mds_session *session)
@ -4024,7 +4022,9 @@ static void check_new_map(struct ceph_mds_client *mdsc,
oldstate != CEPH_MDS_STATE_STARTING)
pr_info("mds%d recovery completed\n", s->s_mds);
kick_requests(mdsc, i);
mutex_unlock(&mdsc->mutex);
mutex_lock(&s->s_mutex);
mutex_lock(&mdsc->mutex);
ceph_kick_flushing_caps(mdsc, s);
mutex_unlock(&s->s_mutex);
wake_up_session_caps(s, RECONNECT);